Are they 'tmpfs' dsiks indispensable?
There are many disk spaces named 'tmpfs' or 'devtmpfs', which consumes each of 8.4G space! Is It not recommend to delete them and expand the main disk space(/dev/root) as much space as they would be deleted? Are they inevitable to keep Linode's system or Linux system?
tmpfs is a temporary file storage paradigm implemented in many Unix-like operating systems. It is intended to appear as a mounted file system, but data is stored in volatile memory instead of a persistent storage device. devtmpfs is an improved devfs.
devfs is an alternative to "real" character and block special devices on your root filesystem. Kernel device drivers can register devices by name rather than major and minor numbers. These devices will appear in devfs automatically, with whatever default ownership and protection the driver specified. A daemon (devfsd) can be used to override these defaults. devfs has been in the kernel since about 2.3.50.
However, devfs is obsolete…hence devtmpfs… The purpose of devtmpfs is to boost boot-time. devtmpfs is more like tmpfs than devfs. The mount-point is /dev/. devtmpfs only creates device files for currently available hardware on the local system.
Since tmpfs and devtmpfs are located in RAM, you can't delete them…